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Published in Les Goring, Residential Surveying Matters and Building Terminology, 2023
Moisture barrier: This is also referred to as a vapour barrier. Its function is to inhibit the diffusion of moisture-movement from one structural element to another. Materials used for this are usually of plastic- or polyethylene-sheeting.
Application of hygrothermal analyses to optimise exterior wall design
Published in J. Carmeliet, H. Hens, G. Vermeir, Research in Building Physics, 2020
P. Mukhopadhyaya, K. Kumaran, M. Rousseau, F. Tariku, D. van Reenen, A. Dalgliesh
The vapour barrier is the last effective component of the wall in protecting the indoor room environment from the influence and fluctuation of the moisture content in the outdoor climate. This study considers three vapour barriers (I, II and III), representing three different water vapour diffusion control levels (Fig. 11).
Understanding air barriers in mechanically attached low slope roofing assemblies for wind uplift
Published in Paul Fazio, Hua Ge, Jiwu Rao, Guylaine Desmarais, Research in Building Physics and Building Engineering, 2020
A. Baskaran, S. Molleti, R.J. Booth
In general airflow control is achieved by the installation of an air barrier system. One of the system mitigation functions of the air barrier system in MAA is to minimize air leakage through the roofing system and thereby reduce membrane flutter and associated fatigue. In cold climates the air barrier system can also reduce condensation by impeding transfer of air borne moisture into the system. The term air barrier system and vapour barrier (retarder) are sometimes misunderstood. Vapour control is achieved through a material, which is a vapour barrier, while the airflow control is achieved by the application of air barrier materials and by sealing joints and junctions, which altogether form an air barrier system. Sometimes attempts have been made to achieve the requirements of both (air and vapour control) by using one material (Quirouette, 1985). However the component properties and system performance should be considered before deciding that one material can do double duty of air and vapour control. The Canadian Roofing Contractor’s Association’s Specification Manual considers materials for air and vapour control separately (CRCA, 2002).
Comparison of model numerical predictions of heat and moisture transfer in porous media with experimental observations at material and wall scales: An analysis of recent trends
Published in Drying Technology, 2019
Thomas Busser, Julien Berger, Amandine Piot, Mickael Pailha, Monika Woloszyn
Kalamees and Vinha compared the results of several tools (1D-HAM,[97] MATCH[98] and WUFI-2D) with experimental tests.[19] The test equipment was composed of a wall located between two chambers simulating two different climatic conditions, either constant or cycling. The wall structures were composed of different insulation materials (mineral wool, cellulose insulation and sawdust insulation), a vapor barrier (plastic sheet or bitumen paper) and sheathing. All the properties of the materials used were measured (thermal conductivity, permeability, density, moisture storage function). Three walls were presented in detail in.[99] The predictions of all three software programs were close for all test wood-frame walls. The differences were greater for cyclic conditions than stationary conditions (13 versus 5%, respectively, for maximum differences for relative humidity). The authors suggest that the difficulties simulating the hygrothermal behavior correctly with rapidly varying boundary conditions were due to inaccurate determination of material properties. In[19] the authors also emphasized the importance of the initial condition, especially, for moisture content. In this study it was difficult to compare the results between walls and to distinguish the behavior of hygroscopic and non-hygroscopic insulation because the type of vapor barrier differed and the interior finishing influenced the results. Additional investigations of wall assemblies with vapor-tight sheathings were also conducted in.[99] The drying experiment carried out showed that considering the capillary flow improved the results for high relative humidity (>90%), but has a lesser influence for non-hygroscopic insulation (fiberglass) as well as for the transfer dynamics, still under-estimated.